The posi-temp doesn't need air chambers or hammer arrestors.
It's not a quick closing valve.
Quick closing valves are
Most codes call for hammer arrestors, not air chambers.
If you use an air chamber on the valve, you can use tees.
I've used 3/4x1/2x1/2 tees, with a 18" 3/4" pipe and 3/4" cap.
It's not code anymore, but will work until it waterlogs, which is pretty quick.